cloudsolutions-atoms/lib/views/widgets/timer/app_timer.dart

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:test_sa/models/timer_model.dart';
import 'package:test_sa/views/app_style/colors.dart';
import 'package:test_sa/views/app_style/sizing.dart';
class AppTimer extends StatefulWidget {
  final TimerModel timer;
  final Future<bool> Function(TimerModel) onChange;
  final TextStyle style;
  const AppTimer({
    Key key,
    this.timer,
    this.onChange,
    this.style,
  }) : super(key: key);

  @override
  State<AppTimer> createState() => _AppTimerState();
}

class _AppTimerState extends State<AppTimer> {
  Timer _timer;
  DateTime _startAt;
  DateTime _endAt;
  int _delay = 0;
  bool _running = false;
  bool _loading = false;
  final ValueNotifier<String> _period =  ValueNotifier("0:00:00");

  _startTimer() async {
    if (!_running) {
      final time = DateTime.now();
      bool result = await widget.onChange(
          TimerModel(startAt: time,endAt: null,durationInSecond: _delay));
      if(!result) return;
      _running = true;

      if(_endAt != null){
        _delay += _endAt.difference(_startAt).inSeconds;
      }
      _startAt = time.subtract(Duration(seconds: _delay));
      _endAt = null;
    }

    _timer = Timer.periodic(const Duration(seconds: 1), (timer) {
      if(_loading == true) return;
      _period.value = (_endAt ?? DateTime.now()).difference(
         _startAt
      ).toString().split(".").first;
    });
  }

  _stopTimer() async {
    final time = DateTime.now();
    final tempStartAt = _startAt.add(Duration(seconds: _delay));
    bool result = await widget.onChange(
        TimerModel(startAt: tempStartAt,endAt: time,durationInSecond: _delay));
    if(!result) return;
    _running = false;
    _endAt = time;
    _startAt = tempStartAt;
    _timer?.cancel();
  }

  _onPressed() async {
    _loading = true;
    setState(() {});
    if(!_running){
      await _startTimer();
    }else{
      await _stopTimer();
    }
    _loading = false;
    setState(() {});
  }

  @override
  void initState() {
    _startAt = widget.timer?.startAt;
    _endAt = widget.timer?.endAt;
    _running = _startAt != null && _endAt == null;
    _delay = (widget.timer?.durationInSecond ?? 0);
    final difference = _startAt == null ? 0:
        (_endAt ?? DateTime.now())?.difference(_startAt)?.inSeconds ?? 0;
    _period.value = Duration(seconds: _running ? difference : _delay + difference).toString().split(".").first;
    super.initState();
    if(_running){_startTimer();}
  }

  @override
  void dispose() {
    super.dispose();
  }
  @override
  Widget build(BuildContext context) {
    return SizedBox(
      width: 100 * AppStyle.getScaleFactor(context),
      height: 28 * AppStyle.getScaleFactor(context),
      child: ElevatedButton(
        style: ElevatedButton.styleFrom(
          minimumSize: const Size(1, 1),
          padding: EdgeInsets.all(4 * AppStyle.getScaleFactor(context)),
          backgroundColor: _running ? AColors.green[300] : AColors.grey,
          foregroundColor: Colors.black
        ),
        onPressed: _loading ? null : _onPressed,
        child: _loading ? const SizedBox.square(
            dimension: 18,child: CircularProgressIndicator(color: Colors.white,)):
        Row(
          children: [
            Icon(_running ? Icons.pause : Icons.play_arrow),
            Expanded(
              child: Center(
                child: ValueListenableBuilder<String>(
                  valueListenable: _period,
                  builder: (context,value,_){
                    return Text(value,
                      style: widget.style,
                    );
                  }
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}